The Usefulness of 3D Quantitative Analysis with Using MRI for Measuring Osteonecrosis of the Femoral Head

PURPOSE: We wanted to evaluate the usefulness of MRI 3D quantitative analysis for measuring osteonecrosis of the femoral head in comparison with MRI 2D quantitative analysis and quantitative analysis of the specimen. MATERIALS AND METHODS: For 3 months at our hospital, 14 femoral head specimens with osteonecrosis were obtained after total hip arthroplasty. The patients preoperative MRIs were retrospectively reviewed for quantitative analysis of the size of the necrosis. Each necrotic fraction of the femoral head was measured by 2D quantitative analysis with using mid-coronal and mid-sagittal MRIs, and by 3D quantitative analysis with using serial continuous coronal MRIs and 3D reconstruction software. The necrotic fraction of the specimen was physically measured by the fluid displacement method. The necrotic fraction according to MRI 2D or 3D quantitative analysis was compared with that of the specimen by using Spearman's correlation test. RESULTS: On the correlative analysis, the necrotic fraction by MRI 2D quantitative analysis and quantitative analysis of the specimen showed moderate correlation (r = 0.657); on the other hand, the necrotic fraction by MRI 3D quantitative analysis and quantitative analysis of the specimen demonstrated a strong correlation (r = 0.952) (p < 0.05). CONCLUSION: MRI 3D quantitative analysis was more accurate than 2D quantitative analysis using MRI for measuring osteonecrosis of the femoral head. Therefore, it may be useful for predicting the clinical outcome and deciding the proper treatment option.

Contrast-Enhanced Fat-Suppression MR Imaging of Avascular Necrosis of Femoral Head

PURPOSE: To evaluate the findings and role of contrast-enhanced fat suppression MR imaging in avascular necrosis(AVN) of the femoral head. MATERIALS AND METHODS: In 15 patients with AVN of the femoral head, MR T1-weighted and T2-weighted images and contrast-enhanced fat-suppression T1-weighted images were obtained, and the findings were re-viewed. Early and advanced groups were classified on the basis of clinical findings and imaging, and the en-hancement pattern was classified as either type I, rim enhancement; type II, surrounding diffuse enhance-ment; type III, intralesional enhancement; or type IV, II + III. RESULTS: Twenty-four cases of AVN of the femoral head were detected; in nine patients, lesions were bilateral. Eight cases occurred in the early group and 16 in the advanced. All eight in the early group showed the "double line sign" on T2-weighted images, with a type-I enhancement pattern. In the advanced goup, type II(8/16) and type IV(8/16) enhancement patterns were seen. Among the cases showing the type-IV pattern, the intrale-sional enhancing area showed low signal intensity on T1-weighted images and isosignal intensity on T2 weighted in one case, and low signal intensity on T1-weighted images and high signal intensity on T2-weight-ed in the other cases. There was no difference in the extent of the disease before and after enhancement. CONCLUSION: Contrast-enhanced fat-suppression MR images may be helpful in evaluating the extent of AVN of the femoral head and predicting the histopathologic findings of the disease

Avascular Necrosis of the Femoral Head after Renal Transplantation

PURPOSE: To determine the incidence of avascular necrosis (AVN) of the femoral head after renal transplantation, evaluate plain radiographic and MR findings, and compare known predisposing factors between the AVN group and the control group. MATERIALS AND METHODS: Between August 1990 and June 1998, 256 renal transplantations were carried out at the Maryknoll hospital. The incidence of AVN was determined clinically, and in the AVN group, plain radiographic and MR findings were evaluated. A control group of 29 cases was randomly selected from among the remaining 241 patients, and acute rejection, mean daily steroid dose and osteopenia were compared between the AVN group and the control group. RESULTS: The incidence of AVN of the femoral head was 5.9 %(15/256). Involvement was bilateral in nine cases and unilateral in six and 24 femoral heads were thus affected. The mean period required for diagnosis of this condition was 10.7 months(within 6 months: 2 hips, between 6 -12 months: 10, between 12 -24 months: 9, over 24 months: 3). Plain radiographs showed that three cases were Ficat stage I, five were stage II, seven were stage III, and nine were stage IV. MRI indicated that 15 cases were Mitchell class A, one was class C, and three were class D. Correlation between Ficat stage and the period required for diagnosis showed that the longer the latter, the higher the Ficat stage. A comparison of risk factors between the AVN group and the control group showed that the incidence of acute rejection and osteopenia, and the mean daily steroid dose, were higher in the AVN group than in the rejection group and that the difference was statistically significant. CONCLUSION: The incidence of AVN of the femoral head after renal transplantation was 5.9 %. The longer the period required for diagnosis of AVN, the higher the Ficat stage. A comparison of risk factors between the AVN group and the rejection group showed that the incidence of acute rejection and osteopenia as well as the mean daily steroid dose, were higher in the AVN group than in the rejection group, and these may thus be pre-disposing factors for AVN. In patients with these risk factors, even though plain radiographic findings are normal, MRI is necessary if AVN is to be diagnosed during its early stages.

Measurement of Necrotic Portion in Legg-Clave-Perthes Disease: Comparison of MRI Volume Measurement Method andCatterall Classification

PURPOSE: The purpose of this study was to evaluate the extent of necrosis of the femoral head inLegg-Clave-Perthes (LCP) disease. This involved the use of MRI, followed by volume measurement and the use of theCatterall classification system; the difference between the grade obtained using each of these approaches was thendetermined. MATERIALS AND METHODS: We retrospectively reviewed 28 hip-joint MR images on which a diagnosis of LCPdisease had been based. According to the necrotic portion of femoral head, and on the basis of the catterallclassification, LCP was graded 1 to 4, as follows: Grade I=0~ <25%; II=2 5~ <50%; III=50~ <75; IV=75-100%. Using atransparent paper on which 1mm squares had been drawn, the necrotic area of each MR image was measured; thefollowing equation was then used to calculate the volume of the necrotic portion: volume=necrotic area x slicethickness. On the basis of this measurement, each femoral head was graded and the results were compared with thoseobtained using the Catterall classification. RESULTS: In 24 joints(85.7%), grades according to the Catterallclassification and MRI volume measurement were not the same. As compared with the volume measurement method, useof the Catterall classification led to grade overestimation in 18 joints (64.3%) and underestimation in six(21.4%). CONCLUSION: The grade according to the Catterall classification was different from that obtained usingthe volume measurement method. This study thus indicates the need for a new system of classifying LCP diseasebased on the volume measurement method and using MR imaging.

Early Avascular Necrosis of the Femoral Head: Relationship of the Findings of Preoperative MRI and the Long-Term Results of Core Decompression

PURPOSE: To evaluate potential correlation between the extent and site of avascular necrosis (AVN), as determined by preoperative magnetic resonance (MR) imaging, and the development of femoral head collapse. MATERIALS AND METHODS: Using clinical, radiographic and MR imaging criteria, twenty hips in 15 patients were selected for core decompression. Preoperative MR results were classified into three categories: group A, less than 15% involvement of the weight-bearing portion of the femoral head; group B, 15%-30% involvement; group C, more than 30% involvement, according to ARCO staging. We also established three groups according to site of involvement of the femoral head, namely medial, middle and lateral. RESULTS: Of 20 cases, three were stage Ia; two, Ib; four, Ic; three, IIa; two, IIb; and 6, IIc. Ten cases of Ia, Ib, IIa or IIb showed no femoral head collapse during follow-up of at least 24 months, while ten cases of Ic or IIc showed femoral head collapse. CONCLUSION: The prognosis of core decompression in patients with early AVN is related to the area of lesion in the femoral head.